With the Six Nations set to kick-off this weekend, the British & Irish Lions coaches will be keeping a watchful eye on proceedings as they look to finalise their squad ahead of this summer's tour to Australia.

This week's Scrum Sevens looks at a group of key match-ups which will hopefully materialise during the Six Nations, injuries permitting, and which could go a long way to helping Lions boss Warren Gatland make his mind up.

Both travelled with the Lions in 2009 on the tour of South Africa but four years ago it was a straight shootout between Kearney and Lee Byrne for the No.15 shirt. Byrne started the first Test but Kearney got the nod for the second and third while Halfpenny suffered an early thigh injury which cut short his tour. Byrne is still very much in the mix for a place on the plane to Australia but the smart money would be on Kearney or Halfpenny to be starting at fullback.

Halfpenny has had a huge season for the Blues and continued his impressive form last term which saw him become an integral part of the Wales team that scooped the 2012 Six Nations. Despite their woeful autumn series, he emerged with his reputation intact and propelled his way into the Lions reckoning once again. Kearney's season has been blighted with injury but if he is fit, then he will be one of the first names on the Ireland team sheet. Their match up on Saturday should be fascinating.

This is shaping up as perhaps the hardest decision Gatland will have to make when he sits down to pick his XV for the first Test against the Wallabies on June 22 in Brisbane. Both are outstanding tight-heads and offer similar qualities - there is very little between them. In terms of recent international form, however, there are some stark differences. Jones missed the autumn internationals through injury but, in contrast, Cole sat out just 22 minutes of England's four games.

While the two props will not literally clash heads when they meet on the field, there will be a fair few keeping their eyes on how the pair fair. Jones has the benefit of 83 caps for Wales under his belt and also two Test caps from the brutal 2009 Lions series while Cole, six years Jones' junior, is on 35 for England. The pair will definitely, we expect, travel to Australia but it would take a brave man to pick one above over the other. The pair should meet in their team's final match of the Six Nations on March 16 - hopefully the organisers are keeping the best clash until last, both on the field and in the scrum.

Wales' Richard Hibbard and England's Tom Youngs may have something to say about this match up, but Hartley and Best are still the leading contenders to claim a place in the Lions' squad. What may count against Hartley, however, is his ill-discipline. Hartley has already served a ban this season, ironically for striking Best during a Heineken Cup match, and has a history of toeing the disciplinary tightrope and sometimes falling foul of the citing commissioner.

He missed the autumn internationals due to injury and his absence allowed Youngs to stake his claim for the Test hooker shirt. But Hartley is a favourite of the England coaching staff and for Northampton, Jim Mallinder has also invested his trust with the hooker their current captain. Best has also captained Ulster on occasions and has been a shining light in their hugely impressive season. If Hartley gets the nod at hooker for England then the two should meet on February 10 in Dublin.

Heaslip said he could have kissed Declan Kidney when he was named Ireland skipper so if Gatland decides the No.8 should captain the Lions, then God knows how the Irishman will react. The Leinster back-row played all three of the Lions Tests in 2009 and that experience will put him in good stead for the summer's jaunt to Australia. He is playing some great rugby for both club and country and his name is being mentioned in the same breath as Sam Warburton, Brian O'Driscoll and Chris Robshaw as potential Lions captains.

But standing in Heaslip's way for the No.8 Test jersey is Wales' Toby Faletau. He played all four of their autumn Tests and sat out just 15 minutes of their 2012 Grand Slam triumph. And being just 22 there is every chance that Faletau could get three Lions tours under his belt over the next eight years. While the pair are likely to travel in the summer, it is unclear who will get the starting jersey - Wales' clash with Ireland on Saturday could help the decision makers.

While Sam Warburton gets the nod for Wales at openside on Saturday, do not rule out Justin Tipuric also travelling Down Under. The battle for the No.7 shirt is set to go right to the wire with Toulon's Steffon Armitage and Ireland's Sean O'Brien also laying some claim to the back-row spot. But when Sam Warburton eventually comes into contact with England's inspirational skipper in the final game of the Six Nations then it could go a long way to decide who gets the openside shirt next summer and maybe even the captaincy.

Robshaw has been a breath of fresh air for England since he took the captaincy just over a year ago and his impressive marshalling of the All Blacks back-row in December would not have gone unnoticed by Gatland. There is likely to be space for all three - Warburton, Tipuric and Robshaw - on the plane to Australia but there is probably room for just one in the Lions' Test back-row.

As things stand, Sexton is the clear favourite to guide the Lions from fly-half in the summer. The outstanding No.10 has helped Leinster to back-to-back Heineken Cup triumphs over the past two seasons and has frequently excelled for Ireland. But following the news that he will leave Ireland at the end of the season, it remains to be seen if he will be distracted by the off-field furore regarding his playing future.

If the unthinkable does happen and Sexton's stock drops in the Six Nations, then Owen Farrell is probably the next in line. One of the world's four best players, according to the shortlist for last year's IRB Player of the Year award, Farrell shone against the All Blacks for England and also excelled for Saracens during their Heineken Cup campaign. His place in the Lions squad is by no means certain but he has the big-game mentality to force his way into the reckoning and maybe even the Test squad. The two will probably meet on February 10 at the Aviva Stadium - it should be fascinating.

The battle for the England scrum-half berth is up in the air but Lancaster has opted for Ben Youngs for their opening match with Scotland on Saturday. It was Youngs who started against the All Blacks back in December but Care has probably received more media coverage for his recent performances than his Leicester counterpart. Phillips, who started all three Tests for the Lions in 2009, looks set to be Wales' first choice No.9 throughout the tournament and all three should travel to Australia in the summer.

With Phillips' Bayonne side out of Europe, this will be the only chance Gatland gets to see the scrum-halves come up against each other before he picks his Lions squad. Gatland is no stranger to the Welsh No.9 having coached him during his tenure in charge of the team but he may opt for that bit of added pace that the England duo bring. Speculation aside, the match on March 16 will no doubt help Gatland's mindset in one way or another.